The Nissan Leaf has taken the lead from the Chevy Volt in U.S. electric car sales, despite a slow start to production and difficulties in acquiring cars for American consumers due to the earthquake and tsunami that hit Japan in March.

In a battle of the greenest, most fuel-efficient cars on the market, the diminutive all-electric Leaf has had 3,708 cars delivered so far this year, compared to the almost-all-electric Volt’s 2,745. Nissan and Chevy said that they each expect to sell 12,000 by the end of 2011.

Although there’s growing demand for the gas-sipping cars, the base sticker price of the vehicles before government incentives — $33,000 for the Leaf and $41,000 for the Volt— keeps them beyond the reach of what many U.S. consumers can afford.

Although the resulting sales figures are small, George Peterson, an analyst with the California-based consulting firm AutoPacific, said that may be the way Nissan and Chevy want it for now. “From a sales standpoint, Nissan and Chevrolet have been very cautious, wanting to make sure these vehicles are as bulletproof as possible, taking time to thoroughly inspect and check everything,” Peterson said.

Peterson said that he expects sales of electric vehicles like the Leaf and Volt to increase to about 3 percent of total car sales and that the cars will remain a niche purchase. “We’re not going to see hundreds of thousands of these on the road,” Peterson said.